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                <div class="container"><article class="page"><h1 class="post-title animated flipInX">区块链安全</h1><div class="post-meta">
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                    <i class="fas fa-user-circle fa-fw"></i>ChenDong Zhu
                </a>&nbsp;<span class="post-category">收录于&nbsp;<i class="far fa-folder fa-fw"></i><a href="/categories/%E5%AD%A6%E4%B9%A0/">学习</a>&nbsp;</span></div>
            <div class="post-meta-other"><i class="far fa-calendar-alt fa-fw"></i><time datetime=2020-01-01>2020-01-01</time>&nbsp;
                <i class="fas fa-pencil-alt fa-fw"></i>约 2138 字&nbsp;
                <i class="far fa-clock fa-fw"></i>预计阅读 5 分钟&nbsp;</div>
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                <h2 class="post-toc-title">目录</h2>
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  <ul>
    <li><a href="#1-区块链安全隐私与性能问题研究综述">1 区块链安全、隐私与性能问题研究综述</a>
      <ul>
        <li><a href="#文章贡献创新点">文章贡献/创新点</a></li>
        <li><a href="#文章内容笔记">文章内容笔记</a>
          <ul>
            <li><a href="#区块链的核心技术">区块链的核心技术</a></li>
            <li><a href="#对等网络">对等网络</a></li>
            <li><a href="#密码学">密码学</a></li>
            <li><a href="#共识机制">共识机制</a></li>
            <li><a href="#智能合约">智能合约</a></li>
            <li><a href="#区块链安全">区块链安全</a>
              <ul>
                <li><a href="#对等网络-1">对等网络</a></li>
                <li><a href="#共识机制-1">共识机制</a></li>
                <li><a href="#智能合约-1">智能合约</a></li>
              </ul>
            </li>
            <li><a href="#区块链隐私">区块链隐私</a></li>
            <li><a href="#区块链性能">区块链性能</a></li>
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  <ul>
    <li><a href="#1-区块链安全隐私与性能问题研究综述">1 区块链安全、隐私与性能问题研究综述</a>
      <ul>
        <li><a href="#文章贡献创新点">文章贡献/创新点</a></li>
        <li><a href="#文章内容笔记">文章内容笔记</a>
          <ul>
            <li><a href="#区块链的核心技术">区块链的核心技术</a></li>
            <li><a href="#对等网络">对等网络</a></li>
            <li><a href="#密码学">密码学</a></li>
            <li><a href="#共识机制">共识机制</a></li>
            <li><a href="#智能合约">智能合约</a></li>
            <li><a href="#区块链安全">区块链安全</a>
              <ul>
                <li><a href="#对等网络-1">对等网络</a></li>
                <li><a href="#共识机制-1">共识机制</a></li>
                <li><a href="#智能合约-1">智能合约</a></li>
              </ul>
            </li>
            <li><a href="#区块链隐私">区块链隐私</a></li>
            <li><a href="#区块链性能">区块链性能</a></li>
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            </div><div class="post-content"><a class="post-dummy-target" id="1-区块链安全隐私与性能问题研究综述"></a><h2>1 区块链安全、隐私与性能问题研究综述</h2>
<ul>
<li>
<p>DOI:10.13196/j.cims.2021.07.022</p>
</li>
<li>
<p>作者:曹雪莲，张建辉，刘波</p>
</li>
</ul>
<a class="post-dummy-target" id="文章贡献创新点"></a><h3>文章贡献/创新点</h3>
<ul>
<li>基于区块链层次结构与运行原理，就对等网络、共识机制和智能合约层面的安全问题及攻防措施进行分析评估</li>
<li>基于区块链隐私威胁基本原理，比较分析不同隐私保护对象的分级隐私保护策略</li>
<li>通过分析性能制约因素，评估基于链上与链下两种扩容路线的最新研究进展</li>
<li>针对安全、隐私和性能的现存问题，提出可能的解决思路并指出未来研究方向</li>
</ul>
<a class="post-dummy-target" id="文章内容笔记"></a><h3>文章内容笔记</h3>
<a class="post-dummy-target" id="区块链的核心技术"></a><h4>区块链的核心技术</h4>
<p>区块链是一种<font color="red">按时间顺序</font>，将包含有效交易的数据区块连接形成的链式数据结构，并以<font color="red">密码学</font>方式保证不可篡改和不可伪造的去中心化共享账本；利用密码学产生的链式数据结构来存储和验证数据，利用<font color="red">对等网络和共识机制</font>来生成和更新数据，利用脚本代码(<font color="red">智能合约</font>)操作数据</p>
<a class="post-dummy-target" id="对等网络"></a><h4>对等网络</h4>
<ul>
<li>在对等节点之间分配任务和工作负载的分布式应用架构，是对等计算模型形成的一种组网技术或网络通信形式</li>
<li>网络中<font color="red">不存在中心权威节点</font></li>
</ul>
<a class="post-dummy-target" id="密码学"></a><h4>密码学</h4>
<p>运用哈希函数，非对称加密技术等多种密码学技术来保证区块链的完整、不可篡改及可校验等特性</p>
<a class="post-dummy-target" id="共识机制"></a><h4>共识机制</h4>
<blockquote>
<p>如何使信任关系薄弱的节点针对区块有效性达成一致意见，并保存一致的数据副本使区块链中的<font color="red">共识问题</font></p>
</blockquote>
<p>共识机制主要解决两个问题：</p>
<ul>
<li>区块数据写入</li>
<li>区块同步</li>
</ul>
<p>共识机制的目标</p>
<ul>
<li>一致性，所有诚实节点保存的区块链的前缀部分完全相同</li>
<li>有效性，某诚实节点发布的信息终将被其他所有诚实节点记录在自己的区块链中</li>
</ul>
<a class="post-dummy-target" id="智能合约"></a><h4>智能合约</h4>
<ul>
<li>公开透明，任何节点都可以查看合约代码</li>
<li>不可更改，区块链保证存储数据的不可篡改性</li>
<li>可自动执行，外部时间触发预设条件后，智能合约按照预先封装的响应规则进行相应操作</li>
<li>（利用虚拟机作为智能合约执行环境来对合约调用所需资源进行隔离和限制）</li>
<li>（智能合约编程语言以领域专用语言为主，如Solidity）</li>
</ul>
<p>区块链的智能合约使部署在区块链上的<font color="red">可共享程序代码</font>，它封装了预定义的若干状态、转换规则、触发条件和响应规则，可在不依赖任何中心机构的情况下被多个节点执行，并<font color="red">得到各参与方认可的执行结果</font></p>
<a class="post-dummy-target" id="区块链安全"></a><h4>区块链安全</h4>
<p>主要针对<font color="red">对等网络、共识机制和智能合约</font>(密码学隐患较小)</p>
<a class="post-dummy-target" id="对等网络-1"></a><h5>对等网络</h5>
<p><strong>威胁</strong></p>
<ul>
<li>攻击者通过拓扑结构获取目标节点的路由信息，并伪造多个身份活干扰路由以阻碍目标节点与其余节点通讯，即<font color="red">拓扑结构引发的安全问题</font></li>
<li>增加对等节点之间的通信传输延迟而影响共识，即<font color="red">传输延迟问题</font></li>
</ul>
<p>（日蚀攻击，女巫攻击，克隆攻击）</p>
<p><strong>对策</strong></p>
<p>针对拓扑结构引发的问题</p>
<ul>
<li>限制节点创建</li>
<li>设置节点间的链接</li>
<li>增加连接选择</li>
<li>异常检测机制</li>
</ul>
<p>（确定性随机驱逐过程，试探连接，驱逐前验证，设置节点TCP连接上限、IP地址和椭圆曲线数字签名密钥一一映射）</p>
<p>针对传输延迟问题</p>
<ul>
<li>多种中继网络如:FIBRE,Falcon,SABRE</li>
<li>(一定程度减少了传输延迟，但仍有问题)</li>
</ul>
<a class="post-dummy-target" id="共识机制-1"></a><h5>共识机制</h5>
<ul>
<li><font color="red">工作量证明/权益证明共识机制</font>假设攻击者掌握不超过全网一般的算力/权益时系统是安全的</li>
<li><font color="red">实用拜占庭容错共识机制</font>可容忍不超过三分之一的节点失效或恶意节点</li>
</ul>
<p><strong>威胁</strong></p>
<ul>
<li>（网络中心化）51%攻击：节点聚集算力/权益形成的矿池使51%攻击成为可能</li>
<li>（偏离共识规则的策略）利用矿池对区块生成情况和其余矿池算力等信息，使用偏离共识规则的策略
<ul>
<li>自私挖矿策略（计算出新区块后择机公布）</li>
<li>区块截留策略（部分节点入侵其余矿池）</li>
</ul>
</li>
<li>（共识机制的缺点）实用拜占庭容错共识机制和一些新共识机制<font color="red">依赖一些特殊节点</font></li>
</ul>
<p><strong>对策</strong></p>
<ul>
<li>（网络中心化，多是理论研究，难以有效应用）
<ul>
<li>SMART-POOL避免形成大矿池</li>
<li>利用博弈论和机器学习，实时监测节点间潜在的合作行为</li>
<li>矿池“关闭”策略</li>
</ul>
</li>
<li>（偏离共识规则的策略）
<ul>
<li>不同影响因素下各种策略的盈利能力以及共识工程中对此类策略的检测并提出对策</li>
</ul>
</li>
<li>（共识机制的缺点）
<ul>
<li>引入奖励机制</li>
<li>改变区块结构设计</li>
</ul>
</li>
</ul>
<a class="post-dummy-target" id="智能合约-1"></a><h5>智能合约</h5>
<p><strong>威胁</strong></p>
<ul>
<li>不安全的合约编程，编程语言本身的缺陷，编程人员对编程语言的理解偏差</li>
<li>不可靠的合约执行，执行环境和执行数据的安全性</li>
</ul>
<p><strong>对策</strong></p>
<p>合约编程&amp;合约执行环境</p>
<ul>
<li>使用通用编程语言如JAVA、GO</li>
<li>提出新的领域专用语言</li>
<li>符号执行技术</li>
<li>形式化验证技术</li>
<li>模糊测试技术</li>
<li>利用博弈论、深度学习进行安全分析</li>
<li>可信硬件</li>
<li>容错合约</li>
</ul>
<p>合约执行数据</p>
<ul>
<li>提供可靠执行数据</li>
</ul>
<a class="post-dummy-target" id="区块链隐私"></a><h4>区块链隐私</h4>
<p>区块链<font color="red">假名机制</font>：利用密码学技术计算出的地址代表用户身份（用户可以生成任意数量的地址，同一用户的不同地址可单独使用且不存在关联关系）</p>
<p>由于区块链中交易数据、合约代码公开，所以可以通过分析数据获得更多隐私</p>
<p><strong>威胁</strong>：主要来源于攻击者对于交易、网络通信、智能合约（计算敏感数据，如拍卖合约中的竞价金额）等信息的恶意窃取和利用</p>
<p><strong>对策</strong></p>
<ul>
<li>交易内容
<ul>
<li>地址混淆机制：不同用户建通过交易来实现资产交换、混淆用户地址的一种隐私保护机制（典型应用CoinJoin）</li>
<li>信息隐藏技术：环签名、零知识证明、同态加密</li>
</ul>
</li>
<li>网络通信
<ul>
<li>混淆网络（如Nym）</li>
<li>洋葱路由技术（保护网络通信的真实发送节点和接受节点，实现节点的匿名通信）</li>
</ul>
</li>
<li>智能合约(这方面还有待改进)
<ul>
<li>结合<font color="red">可信硬件</font>（Ekiden）</li>
<li>密码学中的承诺，可信硬件和零知识证明</li>
</ul>
</li>
</ul>
<a class="post-dummy-target" id="区块链性能"></a><h4>区块链性能</h4>
<ul>
<li>吞吐量远低于VISA</li>
<li>全网存储使数据存储更加困难
<ul>
<li>比特币中完全同步自创世区块至今的所有历史数据需要318.1GB（每年增长61.59GB）</li>
<li>以太坊历史数据604.29GB(每年增长2~3GB)</li>
</ul>
</li>
<li>单链结构使区块链的交易能力受限于单个节点</li>
</ul>
<p><strong>优化方向</strong></p>
<ul>
<li>链上扩容
<ul>
<li>增加区块容量</li>
<li>有向无环图</li>
<li>分片</li>
</ul>
</li>
<li>链下扩容
<ul>
<li>侧链（为某种主链提供支持和服务的区块链）</li>
<li>支付通道</li>
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